The present invention relates to an image processing device having a caption function, and more particularly to a caption display controlling device and the method thereof which can scroll up and display on a screen a caption for several scenes at need.
In a caption image device such as a caption video cassette recorder (VCR), a caption signal can be displayed as caption in a specific position of a display screen by being separated and decoded from a composite video signal having an encoded caption signal in the form of digital data. That is, original words are encoded in the 21st line of an odd field of a video signal and are decoded to be displayed on the top or the bottom of the screen as a caption by selection of viewer (in a closed caption). Meanwhile, to help the understanding of native viewers, captions may be processed by dubbing words written in their native language in a video tape, etc. manufactured in a foreign country. However, in this case, the viewers cannot arbitrarily select the presence of dubbed caption display (in an open caption).
FIG. 1A shows that a caption is displayed in a specific position of the screen by decoding closed caption data included in a composite video signal. That is, in a caption mode, a caption display device divides, for example, a television screen into a total of fifteen lines L1 to L15, and displays a caption in either the top four lines L1 to L4 or the bottom four lines L12 to L15. Also, in a text mode, text data are displayed in the total of fifteen lines L1 to L15 of the screen as shown in FIG. 1B.
Referring to FIG. 2, construction of a conventional caption display device is illustrated. The device has a caption module 1 for decoding caption data from a composite video signal supplied from a television or a VCR to display a caption. And, a video superimposing section 7 is provided for superimposing the caption video signal obtained in the caption module 1 on the original composite video signal to display the superimposed image on the screen. The caption module 1 comprises a caption data extraction section 2 for extracting caption data encoded in the composite video signal, a caption controller 3 for controlling the decoding of the extracted caption data, a sync signal separating section 4 for separating horizontal and vertical sync signals needed for the caption function from the composite video signal, an on-screen display section 5 for constructing a caption to be displayed on the screen under the control of the caption controller 3, and a control logic section 6 for providing operation clocks and signal processing timing control signals for the respective elements.
Operation of a conventional caption display device constructed as above will now be explained with reference to FIGS. 2 and 3.
The caption data extraction section 2 extracts digital caption data encoded in a composite video signal and supplies the extracted data to caption controller 3. Caption controller 3 decodes a caption's display position on a screen, a font, and characters to be actually displayed by decoding caption data composed of a control code and a character code and supplies the decoded result to on-screen display section 5 as on-screen display (OSD) information. On-screen display section 5 includes a video memory (RAM), a font memory (ROM), etc., and stores OSD information assigned by caption controller 3 and also supplies the stored information to superimposing section 7.
That is, in the caption data, the control code is decoded as information indicating the top or bottom four lines among the total fifteen lines on the screen where the caption will be positioned, and also indicating fonts, etc., and the character code is decoded as character information to be actually displayed on the screen. On-screen display section 5 accesses its internal font ROM in accordance with the decoding result of caption controller 3 and supplies the accessed OSD data to superimposing section 7. Superimposing section 7 makes a single video signal by superimposing on the composite video signal a caption OSD signal supplied from on-screen display section 5 and displays the superimposed video signal on the screen.
As described above, the caption can be displayed in the bottom four lines L12 to L15 among the total of fifteen lines L1 to L15 of the screen in the caption mode, as shown in FIG. 1A, and can be displayed, as shown in FIG. 1B, in the overall lines of the screen in the text mode. On-screen display section 5 uses as reference signals the horizontal and vertical sync signals provided from sync separation section 4 and processes OSD data under the timing control of control logic section 6. Accordingly, discrimination is improved by displaying characters of the caption generally with a white color and the background of each existing character with a box in black. That is, only the 1-character parts before and after the character existing part are processed as background, and the other parts of the four lines are processed to be transparent to show the original image.
However, in such a conventional caption display device, words (caption) corresponding to the scene are displayed for a short time in every scene. And, whenever the scene is changed, the words for the previous scene are erased and new words for the new scene are displayed. Accordingly, while watching captioned video, the viewer may watch the next scene without completely understanding the content of words, depending on his language ability. Accordingly, there are problems of inconvenience in watching video and degrading language study efficiency.